Due to the recent advance of information and communication technology, various wireless communication technologies are under development. Among them, wireless local area network (in what follows, ‘WLAN’) is the technology which utilizes wireless frequency technology and supports portable devices to access the Internet wirelessly at home, office, or in a particular service area.
For example, portable devices may include a Personal Digital Assistant (PDA), portable computer (laptop computer), and Portable Multimedia Player (PMP). For most cases, devices of a WLAN system communicate with each other via a management entity such as a base station or an access point (AP). A management entity is responsible for scheduling for data communication.
To secure flexibility of communication among devices of WLAN system, various protocols are being proposed to implement direct communication among devices without involving a management entity. NAN is the specification defined by the WFA (Wi-Fi Alliance), based on the Wi-Fi standard. The NAN specification defines a synchronization and a search procedure among devices in the frequency band of 2.5 GHz or 5 GHz.